For months, really from before Iowa, even, it was clear to most Sanders supporters that there was collaboration going on between the DNC and the Sanders campaign.
Debbie Wasserman Schultz denied it, of course. Now we have solid evidence. Although it’s not always possible to pin down specific actions or even meanings from individual emails (Taco Bowl??) it is clear that large numbers of them have people referencing the campaign in a decidedly less than neutral manner.
Now, the people who’ve been saying there was no election rigging going on; the people who excused Arizona so glibly by saying it was a Republican in charge of the elections; the people who didn’t bat an eye when tens of thousands of people were disenfranchised in New York, and the switching of voter registrations began. There was a lot of that in California, too. There was a whole lot of shit in California. There was fraud in a lot of other states, too.
But Clinton supporters just said ‘well, we’re getting more votes and you’re just sore losers who wear tin-foil hats and are 14 years old.’

Now we have evidence that we were right and they were lying all along, and Hillary supporters are saying “Well, so what? All politicians are corrupt.” or “Well, so what. It’s our party, Bernie’s a newcomer.” The point is if you’d felt like that, you could have just dispensed with these pesky primaries altogether. But, you didn’t. It might have looked bad. Like those show elections that you have now and again in terribly undemocratic states, that’s what it would have looked like.